Equipment for continuously forming concrete barriers of the type commonly referred to as "Jersey" barriers is well known. Such equipment, also known as automated slip formers, generally includes a slidable form or "mule" for defining the shape of the barrier, a hopper coupled to the mule through which concrete is delivered to the mule, and a drive assembly coupled to the mule and hopper for causing these elements, specifically the slidable mule, to move along a path extending next to the surface on which the barrier is to be erected. An exemplary piece of such slip forming equipment is manufactured by Miller Formless Company, Inc., of McHenry, Ill., and is identified by Model No. M-8800.
Known slip forming equipment is well adapted to continuously forming horizontally extending concrete traffic barriers having either smooth outer surfaces or outer surfaces having continuous, horizontally extending grooves, ridges, or other concave or convex surface textures. Unfortunately, known slip forming equipment is not adapted to forming horizontally extending concrete barriers having other than horizontal textures, specifically vertically extending, transversely extending, or other non-horizontally extending surface texturing. This limitation of known slip forming equipment is especially undesirable in areas where state and/or local construction codes require that at least one surface of the concrete road barrier include a non-horizontally extending surface texture. For instance, construction codes in the State of Washington require that, under certain circumstances, the outer surface of concrete barriers installed along the outer edges of bridges include substantially vertically extending striations. At present, such bridge barriers are formed and poured on a non-continuous, section-by-section basis, at a cost far in excess of that for continuously forming horizontally extending concrete barriers of similar height and thickness.
With respect to vertical striations, equipment is known for vertically slip forming concrete abutments, silos, and other structures characterized by vertically extending concrete walls. Accordingly, vertically extending grooves, ridges, or concave or convex surface textures can be placed in the structure according to the vertical direction of form movement. Such equipment is disclosed, for instance, in U.S. Pat. No. 3,453,707 to Johansson, and U.S. Pat. No. 4,314,798 to Pettersson. The Pettersson apparatus includes a yoke and a pair of leg assemblies attached to and extending downwardly from the yoke. The leg assemblies are spaced a predetermined distance from one another, and the apparatus includes means for moving the leg assemblies toward and away from one another. In use, two form halves are positioned between and supported by the leg assemblies. Concrete is then poured between the form halves, which are caused to move upwardly in a continuous manner by moving the yoke and leg assemblies upwardly. Although known apparatus for vertical slip forming may be satisfactorily employed in the fabrication of vertically extending walls, such apparatus are not adapted to form horizontally extending barriers, or vertically extending walls having other than vertically extending surface texturing.
In addition, surface texturing problems are compounded with respect to slip forming, wherein there is a desire or construction code requirement which stipulates that both sides of the concrete structure have a textured surface, the texture being other than horizontal striations. Such designs would generally include conventional concrete forming methods, wherein forms having the reverse of the textures are fixed in place and properly supported prior to placement of the wet concrete. In this regard, significant bracing including cross-tying between the two form structures is required to adequately support the concrete structure or barrier while the concrete is being poured. The same reinforcement must then be removed once the concrete has substantially cured.
Therefore, there exists a need for a concrete forming system that allows textured patterns to be placed on one or both sides of a substantially vertical extending surface, such as the sides of a concrete barrier. For efficiency and ease of construction, it is beneficial that the forming system incorporate a movable concrete placing system, wherein wet concrete is placed between forms through a drive means, as the drive means continually progresses along the form structure.